The variable valve controller adjusts a valve timing or valve lift of an intake valve in order to improve output of the engine, to enhance fuel economy, and to reduce emission.
JP-2002-213261A shows a start controller utilizing the variable valve controller in which the intake valve timing or intake valve lift is adjusted in such a manner that an intake air flow rate at starting of the engine becomes minimum quantity to ignite air-fuel mixture in a cylinder, so that a cranking vibration is reduced.
JP-2002-188472A shows a start controller in which the intake valve lift is made small until the engine speed reaches a predetermined peak speed. After the engine speed reaches the peak speed, the intake valve lift is made small to increase the intake air flow rate, so that an over shoot of the engine speed is reduced.
Recently, in order to improve startability of the engine, such as reduction of engine vibration, it is necessary to precisely control the engine speed at starting in which engine speed varies every combustion.
Besides, it is necessary to control the intake air flow rate at intake timing in order to control the variation of engine speed by the intake air flow rate. However, the conventional start controller for an engine conducts the intake valve control irrespective of the intake valve timing. Thus, it is hard to precisely control the engine speed of the engine by controlling the intake air flow rate.
JP-10-82332A (U.S. Pat. No. 5,909,720) shows that, in a hybrid vehicle, the intake valve timing is retarded to reduce an effective compression ratio, and then a starter motor conducts cranking of the engine to reduce the vibration at the cranking. After the engine speed reaches a predetermined value, the intake valve timing is advanced to increase the effective compression ratio and then a fuel injection and an ignition of the air-fuel gas are started to generate an initial combustion.
However, such a system is hardly applied to a vehicle which is driven by only the internal combustion engine.